Brake



BRAKE Filed'May 18, 1932 2 sheets-sheet 1 INVENToRs. EUGENE C. CQEEOLL.Cfc? lh( 72-7 V/.oe

A TTORNEY llzatentedlluly 26, 19'38 UNITED STATES PATENT OFFICE y BRAKEEugene G. Carroll and Cecil H. Taylor, South Bend, Ind., assignors toBendix Aviation Corpo- 1 ration, South Bend, Ind., a corporation o!Delaware Application May 18, 1932, Serial N0. 612,137

Claims. (Cl. 18S-152) This invention relates to brake apparatus andWheels and showing the wheel cylinder mounted is shown as applied to ahydraulic brake system. therein;

Heretofore devices for the braking of vehicles Figure 4 is a viewsimilar to Figure 3 showing have either depended upon the manual effortexa modied form of wheel cylinder;

5 erted by the operator as multiplied by various Figure 5 is a viewsimilar to Figures 3 and 4 5 leverage arrangements, or have dependedupon showing a modified arrangement in which two some additional sourceof power either for apwheel cylinders are provided; and plying thebrakes independently or for assisting Figures 6 is a view in verticalsection of a comthe operator in applying the brakes. plete vbrakeutilizing our invention.

In applying brakes through a foot actuated me- In Figure 1 there isshown a chassis of an auto- 10 chanical or hydraulic leverage, the powerconmobile formed with side rails I0 and i2, a front veniently obtainedis limited. Acertain minimum axle I4, a rear axle I6, front wheels I8and 20 movement of the pedal actuated shoes to the supporting the frontaxle J4, and read wheels 22 drum is required in order to provideadequate and 24 supporting the rear axle I8.

clearance when the brake is not applied and on The wheels I8, 20, 22,and 24 are provided with l5 account of the wear of the various parts. Acerbrakes 26 adapted to be operated by wheel cylintain maximum movementof the brake pedal can ders 28 to which liquid under pressure issupplied not be exceeded by reason of the limitations of by branchconduits 30, 32, 34, 36, and a main conthe space in the vehicle and byreason of the limduit 38. The iluid is forced through said conduitsitations of comfort of movement of the operator. by means of a mastercylinder 40 which is oper- 20 Power brakes usually utilize some outsidesource ated through a piston rod 42 by means of a foot of power orutilize the torque created by the pedal 45.

braking action itself for aiding in applying the The master cylinder 48is provided withareserbrakes. The latter class usually include onlymevoir 46 for a reserve supply of uid and with a chanical connections.plunger 48. 'I'he plunger 481s formed with a pair 25 One of the objectsof this invention is to utilize of spaced pistons 50'and 52 providedwith annular the torque created by the braking action eilicientcuppackings 54 and 56 respectively and is pr0 ly for assisting in applyingthe brakes. vided with a forwardly extending concentric pro- A furtherobject of the invention is to utilize jection 58. The cylinder is alsoprovided with a the braking torque developed in a hydraulic brakfixedhead 68 having associated therewith an an- 3G ing system for increasingthe volume of fluid supnular cup packing 62. The forward end of theplied to the wheel cylinders thereof and/or for projection 58 extendsthrough the head 68 and decreasing the volumetric capacity of said wheelthe packing 62. The packing 62 may be preventcylinders, therebydecreasing the volume of fluid ed from substantial movement and held inplace necessary to be displaced by the master cylinder by any convenientmeans. As shown, a tube is 35 and enabling the operator to use higherleverages utilized which contacts at its forward end with in applyingthe brakes, the front of the cylinder and at its rearward end A featureof the invention is a servo wheel Seats Within the annular grOOVe frmedin the cylinder. packing, thus preventing the packing from moving Afurther feature of the invention is the iucorfai in advance `0f the head'60. The cylinder wall 40 oration of a servo wheel cylinder within anoris formed with a constricted Port u normally p0' inary wheel Wundensitioned in advance of the cup packing 56 and with Further objects andfeatures of the invention a' relatively large opening 66 normallycovered by the piston 52, both said port 64 and said opening wm beapparent after a' reading of the submmed 66 leading to the reservoir 46.The forward end 45 specification and claims and afteraconsideration ofthe projection 58 is formed adjacent to the 0f we attafhed drawings inwhich: rear end of the cup 62 with a plurality of ports Figure 1.15 a pmn View of F' chassls of an auto' such as 68 by which liquid may escapefrom the mobile C qulppd Wlth a brakmg System illustratsystem ahead ofthe cup 62 to the portion of the lng 0111' lul/@11109; cylinderrearwardly thereof and thus may escape 50 Figure 2 1S a VIEW in VeltlcalStion and 0n an through the port 64 back to the reservoir to comenlargedScale Showing the master Cylinder 0f pensate the system for temperaturechanges. the Figure 1; Each wheel cylinder 28 is positioned in a drumFigure 3 is a view in vertical section and on an 10 and is connected tobrake shoes 'I2 and 14. 56 enlarged scale showing a fragment of one ofthe Each cylinder is formed of a cylindrical casting 55 18 having thecentral portion formed with a relatively small bore 18 and the outerportions formed with relatively large bores 80 and 8|. Within thecylinders are a pair of cylindrical pistons 82 and 84 having diameterscorresponding to the bore 18 and formed with central projections 86 and88 which are adapted to contact with each other and to limit the inwardmovement of the pistons. Annular cup packings 80 and 82 associated withthe pistons 82 and 84 respectively are held in place by a spring 84.Liquid is supplied to each wheel cylinder from one of the conduits 30,32, 84 and 88 through anopening 88 and serves to spread the pistons 82and 84 which in turn act upon adjustable links 88 and |00 pivotallyconnected to the shoes 12 and 14.

There are also provided in each cylinder 28 annular pistons |02 and |04having diameters substantially corresponding to the bores 80 and 8|.These pistons are normally held in contact with caps |06 and |08 bymeans of relatively strong springs H and maintain the cups |I4 and H6 inoperative association with the pistons |02 and |04 respectively. Thecylinder is formed with a plurality of passages such as ||8, |20, |22and |24 which communicate with each other and allow free passage ofiiuid from the large diameter bores 80 and 8| to the small diameter bore18. Embossments |25 on the backing plate may serve to limit the.eircumferential movement of the shoes 12 and 14.

The cylinder 228 shown in Figure 4, is substantially the sa-me as thecylinder 28 shown in Figure 3. However, the annular cups 280 and 282 aresecured in grooves in the ends of the pistons 282 and 284 and packings326 and 328 are provided for cushioning the contact of the pistons 282and 284 with the pistons 302 and 304. Moreover the pistons 302 and 304are provided with flanges which are adapted to contact with the ends ofthe casting 216. Thus means are provided for limiting the inwardmovement of the pistons 302 and 304 and thus for limiting the amount ofpressure developed by the braking torque and the amount of uid displacedthereby.

Ball check valves shown in the central part of the wheel cylinders ofFigures 3 and 4 are used to prevent the sucking in of air during thebleeding operation.

In Figure the wheel cylinder 628 is provided with a pair of pistons 682and 684 and is connected to the shoes 612 and 614 by means of links 688and 100. There is associated with the cylinder 628 another cylinder 680having a larger diameter and provided with pistons 102 and 104. Thepistons 102 and 104 are normally maintained in engagement with caps 106and 108 and are adapted to be actuated by links 130 and 132- pivotallyconnected to the shoes 612 and 614 respectively. Inward movement islimited by central projections thereon.

In the operation of the structure disclosed, pressure upon the pedal 44acts through the piston rod 42 to move the piston 48 forward thuscutting off the port 64 and the port 68. Liquid trapped ahead of the cup62 is forced to the brakes by means of the projection 58 and thattrapped ahead of the piston cup 56 but rearwardly of the cup 62 isforced past vthe cup 62 and thus also to the brakes'.

As soon as a small quantity of liquid enters each wheel cylinder 28through the port 86, the pistons 82 and 84 are spread apart, moving theshoes 12 and 14 into contact with the drum 10.

75 The wiping action resulting from the rotation of ||2 which also serveto.

the drum causes the braking torque to be exerted upon one or the otherof the links 88 and |00 which thus returnsone of the pistons 82 or 84 tothe position shown and causes the braking torque to act upon one of thepistons |02 or |04'. This forces liquid from one of the large bores 80or 8| through the passages ||8. |20, |22, and |24 to the small bore 18and thus increases the fluid supplied to the small bore and the pressureapplying the shoes to the drum.

Inasmuch as the effective area of the pistons |02 and |04 is greaterthan that of the pistons 82 and 84, during the phase of the brakingaction after the wiping action begins to exert force upon one of thelinks 88 or |00, the latter must move out faster than the former areapproaching each other and the shoes must be wedged more tightly againstthe drum until they can no more be forced against the drum, whereuponthe braking torque anchors upon the liquid in the system. Inasmuch asthe cup 62 prevents liquid from passing the head 60, assuming that thepedal is held stationary, this force does not react upon the plston 52and the cup 56 but is taken solely upon the small diameter vof theforward projection 58. Therefore a relatively small force exerted uponthe pedal is able to hold the brake. If it were necessary to move thepedal farther to increase the braking effect, the full force of theapplication would react on the pedal. However, the force developed bythe servo is sufficient to accomplish any braking possible withoutsliding the wheels, so that in practice no great force ever reacts uponthe pedal. At the same time, inasmuch as some force reacts upon thepedal through the projection 58, the brake is entirely controllable. Theembossments |25 prevent abnormal movements of the shoes.

When the pedal is released the piston 52 and the projection 58 willreturn to the position shown in Figure 1. Since the projection 58 ts inthe partition 60 with an ordinary machine t, liquid will flow backthrough the ports 68 around the projection 58 and also around thepacking 62 and through the ports in the partition 60 to the reservoir46. 'I'hus the pressure acting on the wheel brakes is relieved and thebrakes will release.

The embodiment shown in Figure 4, however, is prefererd to that shown inFigure 3. Therein, the movement inward of the pistons 302 and 304 islimited by the stop as described above and the eiect of the servo orwiping action is to amplify the supply of liquid in the system so thatit is possible to apply the brakes with relatively small movement of themaster piston. Therefore it is possible to use a relatively largeleverage between the pedal and the master cylinder piston.

In the embodiment shown in Figure 5, the combined servo and operatingcylinders are separated. Therefore two separate cylinders 628 and 680are provided. The operation, however, is the same as that describedabove in connection with Figures 1, 2 and 3. However. the movementinward of the piston 102 or 104 as the case may be in cylinder 680forces additional fluid into the motor formed by the cylinder 628 andthus increases the volume of fluid therein.

It is clear that movement of the pedal actuates the plunger 52 to forceliquid through the system to move the friction element into contact withthe drum and that said pedal and plunger, together with the liquid serveas parts of a device for applying said element to the drum at apredetermined ratio comprising the ratio between the force exerted onthe pedal and the applying force acting on the shoes solely as a resultof the force applied to the pedal, the ratio being determined by therelative diameters of the plunger 52 and the pistons 682. Moreover, thefluid serves as an anchor receiving the full braking torque. The

head and the packing 62 serve as means for reducing the ratio of thereaction felt u'pon the pedal to the total torque of the frictionelement to substantially less than the said ratio between the forceinitially exerted on the pedal and the applying force acting on theshoes solely as a result of said force applied to the pedal, thereaction ratio being determined by the relative diameters of the piston58 and the pistons 104. The master cylinder disclosed herein is alsodisclosed and is claimed in a copending application of Eugene G.Carroll, Serial Number 25,720, filed June 10, 1935.

Itis to be understood that the various embodiments of our inventiondescribed above, are for the purpose of illustration only, and variouschanges may be made therein without departing from the spirit and scopeof the invention.

We claim:

l. In a fluid braking system, a pedal, a. wheel cylinder, means forconverting foot power into brake applying pressure, separatemeansassociated with said wheel cylinder fojr converting braking torque intofluid pressure, and means for preventing said fluid pressure fromreacting with full force upon said pedal.

2. In a fluid brake system, a pedal, a master cylinder, a wheelcylinder, connections between said cylinders, means associated with saidmaster cylinder for converting movement of said pedal into fluidpressure, means associated with said wheel cylinder for converting fluidpressure into brake applying force, means associated with said wheelcylinder for converting braking torque into fluid pressure, and meansassociated with said master cylinder for preventing said fluid pressurefrom reacting with full force upon said pedal.

3. In a fluid braking system, a wheel cylinder, a master cylinder,connections between said cylinders, a piston in said master cylinderhaving a relatively large area, a piston in said master cylinder havinga relatively small area, means for moving said pistons to force fluidfrom said master cylinder to said wheel cylinder to apply the brakes,means responsive to brake application for increasing the fluid pressurein said system, and means for preventing said last mentioned increase influid pressure in said system from reacting on said relatively largearea piston.

4. In a fluid braking system, a master cylinder provided with a piston,a wheel cylinder provided with a piston, connections between said mastercylinder and said wheel cylinder, means for operating said mastercylinder piston for forcing fluid under pressure through saidconnections to said wheel cylinder, means associated with said wheelcylinder and operated by the braking torque for applying additionalpressure to the fluid in said system, and means associated with saidmaster cylinder for preventing the pressure produced by said torquereaction from acting upon said master cylinder piston.

5. In a fluid braking system, a master cylinder provided with a piston,a wheel cylinder provided with a piston, connections between said mastercylinder and said wheel cylinder, means for operating said mastercylinder piston for forcing fluid through said connections to said wheelcylinder. means associated with said wheel cylinder and operated by thebraking torque for supplying additional fluid to said wheel cylinder,and means associated with said master cylinder for preventing thepressure produced by said torque reaction from acting upon said mastercylinder piston.

6. In an automotive vehicle, a rotating element, a friction elementassociated with said rotating element, a fluid motor comprising a wheelcylinder having two oppositely acting pistons, means for increasing thepressure of fluid in said fluid motor for acting to apply the frictionelement to the rotating element. means comprising a second wheelcylinder actuated by said friction element for increasing the volume offluid in said fluid motor, and means for limiting said increase involume.

7. In a hydraulic braking system, awheel cylinder, a pair of small areapistons located in said wheel cylinder, a pair of large area pistonslocated in said wheel cylinder, means connected to said small areapistons for utilizing brake applying force transmitted through saidsmall area pistons, means for transmitting braking torque at times toeach of said large area pistons, means connecting the space occupied byfluid acted on by said large area pistons with the space occupied byfluid acting on said small area pistons, and means for limiting themovements of the large area pistons.

8. In an automotive vehicle, a rotating element, a friction elementassociated with said rotating element, a wheel cylinder having a, pairof pistons therein, means for increasing the pressure of fluid in saidwheel cylinder for applying the friction element to the rotatingelement, means comprising another Wheel cylinder for increasing thesupply of fluid to said first named wheel cylinder, and means includingportions of said last named cylinder for limiting said increase in thesupply of fluid.

9. In a hydraulic braking system, a Wheel cylinder, a friction element,a small area piston located in said wheel cylinder, a large area pistonlocated in said wheel cylinder, means connected to said small areapiston for utilizing brake applying force transmitted through said smallarea piston and for transmitting said force to said friction element,means including said last named means and said small area piston fortransmitting braking torque generated by said friction element to saidlarge area piston, and means for connecting the space occupied by fluidacted on by said large area piston with the space occupied by fluidacting on said small area piston.

10. In a braking system a pedal, a rotating drum, a friction elementadapted to be forced into contact with said drum, means connecting saidpedal and said element for applying said element to said 'drum at apredetermined ratio between the force exerted on the pedal and theapplying force acting on the friction -element solely as a result of theforce applied to the pedal and serving as an anchor for receivingsubstantially the full braking torque, and means included as a part ofsaid first named means for reducing the ratio of the reaction of thetorque felt on the pedal to the total torque of the friction element tosubstantially less than the flrst mentioned ratio.

EUGENE G. CARROLL. CECIL H. TAYLOR.

